The search for new pharmacologically active agents by screening natural sources such as plant, microbial, and fermentation products has led to the discovery of many clinically useful drugs that play a major role in the treatment of human diseases. To date, close to 60% of anti-tumor and anti-infective agents available commercially, or in late stages of clinical trials, are of natural product origin.
In the 1960s, the National Cancer Institute initiated a program to screen large collections of compounds, natural or synthetic for anti-tumor activity. These activities lead to the discovery of one of the most significant compounds in the fight against cancer. An extract from a relatively rare Pacific yew (Taxus brevifolia nutt.) showed unique anti-tumor activity. The active principle, paclitaxel (Taxol(trademark), 1) was isolated. Taxol(trademark) is a registered trademark of Bristol-Myers Squibb. Paclitaxel binds to microtubules and inhibits their depolymerization into tubulin. Paclitaxel blocks the cell""s ability to break down the mitotic spindle during mitosis. With the spindle still in place the cell cannot divide into daughter cells. In 1992 the FDA approved paclitaxel for refractory ovarian cancer. Today paclitaxel is used to treat a variety of cancers, including ovarian, breast, non-small lung, and Karposis sarcoma.
Natural paclitaxel was originally isolated from the bark of Taxus brevifolia. This species is slow growing, taking over a hundred years for a young yew to mature. More importantly, paclitaxel occurs in low concentrations, (0.002 to 0.04% per dry weight), primarily in the inner bark of the tree. Deforestation of this particular yew is an obvious concern and poses a problem for replenishing the naturally occurring limited supply of paclitaxel. Since the demand for paclitaxel increases every year, the scientific community has been forced to look for alternative ways of producing paclitaxel.
Alternative methods for the production of paclitaxel include the use of renewable plant parts, nursery production of yew trees, plant cell culture, semi synthesis from other natural taxane precursors, and total synthesis from simple starting materials.
To date, only semi synthetic approaches have found commercial utility. Taxol and Taxotere (2, a chemotherapeutic semi synthetic analog of paclitaxel) are produced commercially by semi synthesis from 10-deacetylbaccatin III (10-DAB III), a natural taxane isolated (0.02 to 0.1% per dry weight) from the needles of the English yew, Taxus baccata. Bristol-Myers Squibb, the sole supplier of paclitaxel in North America and a major world supplier, produces most of its paclitaxel semi synthetically. Nonetheless, this approach has not fulfilled the demand for paclitaxel.
Substantial effort has gone into the total synthesis of paclitaxel and paclitaxel analogs since its discovery three decades ago. To date, five elegant and unique routes to paclitaxel have been reported since the first successful synthetic report by Nicolaou. Because the paclitaxel molecule is structurally complex, the known synthetic processes are costly and have yields that hinder commercial viability.
In as much as plant cell culture has merit for producing a large-scale quantity of paclitaxel, this approach has yet to be scaled up to produce industrial scale quantities. Lengthy and complex cell culture procedures are involved.
The use of cultivable and renewable plant parts, such as the leaves (needles) and stems of Taxus species is currently the most practical and attractive way of increasing the supply of paclitaxel. The needles of several Taxus species, including Taxus canadensis, have been investigated and found to contain paclitaxel in amounts comparable to the bark of Taxus brevifolia. 
Taxus canadensis is an evergreen shrub found in Eastern Canada and Northeastern United States. This species is unique in its taxane content. The needles contain a major taxane, 9-dihydro-13-acetylbaccatin III (9-DHAB III, 4) along with paclitaxel (0.009-0.05%), 10-deacetylbaccatin III (10-DAB III, 6), baccatin III, (5), cephalomannine, (3), and other minor taxanes. The concentration of 9-DHAB III in the needles is reportedly seven to ten times the concentration of paclitaxel. It already appears that 9-DHAB III may become an important precursor to a new class of semi-synthetic chemotherapeutic agents with increased water solubility.
Therefore, a need exists that provides commercial quantities of the above-referenced natural products from readily available renewable sources.
The process of the present invention is simple and cost effective. It provides paclitaxel and other taxanes in high yield and purity on industrial scale. The process of the present invention is more efficient since it provides 9-DHAB III in high yield and purity in a single chromatography step. Furthermore, paclitaxel, cephalomannine and 10-deacetylbaccatin III are obtained in high yield and purity in three chromatography steps, or at best two steps from the crude alcoholic extract without chemical transformation or destruction of any taxane.
The present invention provides methods for mass production of paclitaxel and related taxanes from plants of the genus Taxus (Taxaceae). More specifically, the present invention relates to a simple cost effective method for mass production of GMP paclitaxel, 9-dihydro 13-acetylbaccatin III, 10-deacetylbaccatin III, and cephalomannine from Taxus canadensis. 
The present invention therefore, provides cost-effective processes for mass production of GMP paclitaxel and other related taxanes from a vegetal source or tissue culture particularly, T. canadensis. 
The present invention also provides paclitaxel in high yield and purity. The present invention also produces industrial scale quantities of other taxanes namely, 9-DHAB III, 10-DAB III, and cephalomannine in high yield and purity.